usb: gadget: f_fs: Add unbind event before functionfs_unbind
commit efb6b535 upstream. While exercising the unbind path, with the current implementation the functionfs_unbind would be calling which waits for the ffs->mutex to be available, however within the same time ffs_ep0_read is invoked & if no setup packets are pending, it will invoke function wait_event_interruptible_exclusive_locked_irq which by definition waits for the ev.count to be increased inside the same mutex for which functionfs_unbind is waiting. This creates deadlock situation because the functionfs_unbind won't get the lock until ev.count is increased which can only happen if the caller ffs_func_unbind can proceed further. Following is the illustration: CPU1 CPU2 ffs_func_unbind() ffs_ep0_read() mutex_lock(ffs->mutex) wait_event(ffs->ev.count) functionfs_unbind() mutex_lock(ffs->mutex) mutex_unlock(ffs->mutex) ffs_event_add() <deadlock> Fix this by moving the event unbind before functionfs_unbind to ensure the ev.count is incrased properly. Fixes: 6a19da11 ("usb: gadget: f_fs: Prevent race during ffs_ep0_queue_wait") Cc: stable <stable@kernel.org> Signed-off-by:Uttkarsh Aggarwal <quic_uaggarwa@quicinc.com> Link: https://lore.kernel.org/r/20230525092854.7992-1-quic_uaggarwa@quicinc.com Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
parent
5f99886c
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